KVM systems enable one or more remote computers to access and/or control one or more target computers. The term computer as used herein is non-limiting and refers to any processor or collection of processors, including servers (and groups or racks thereof), processors in appliances such as ATM machines, kiosks, cash registers, set-top boxes, PCs and the like. Early KVM systems used wired connections between the remote and target computers. However, more recently, wireless KVM systems have become available, e.g., from Avocent Corporation, the assignee of the present application.
A typical wireless KVM system connecting a target computer to a remote computer uses two radios, one at the target computer (or at a switch connected thereto) and the other at the remote computer. These systems preferably operate using the 802.11a standard. Prior wireless KVM systems used two omni-directional antennas. However, using this type of antenna limited the range of transmission between the two radios (the wireless transmitter and the wireless receiver) to about 100 feet through three walls and up to 300 feet line-of-sight. Notably, the distance range was limited by the antennas used, and not by issues relating to the 802.11a standard. It is desirable and an object of the present invention to extend the distance between the wireless radios (the Transmitter and the Receiver) in a KVM system, especially 802.11a-based wireless systems.
This invention provides 802.11a radios an efficient, circularly polarized directional antenna.
It is a further object of the present invention that the transmitted and received signal modulation should not be distorted or sacrificed in group delay. Accordingly, a type of frequency independent structure that includes a match of 50 ohms across the operating bandwidth was developed and optimized.